On June 20, 1837, Alexandrina Victoria, heiress presumptive to the throne, became Queen of the United Kingdom of Great Britain and Ireland. Her uncle, King William IV, had expressed his displeasure at the Regency Act of 1830 and, in 1836, had vowed to stay alive until Victoria was 18 years old. This would allow her to assume the throne without a Regent to guide her actions. True to his vow, William died in the early morning hours of June 20. Victoria had turned 18 on March 24.

In her diary, the young Queen wrote: "I was awoke at 6 o'clock by Mamma, who told me the Archbishop of Canterbury and Lord Conyngham were here and wished to see me. I got out of bed and went into my sitting-room (only in my dressing gown) and alone, and saw them. Lord Conyngham then acquainted me that my poor Uncle, the King, was no more, and had expired at 12 minutes past 2 this morning, and consequently that I am Queen."

The paperwork done that day identified her as Alexandrina Victoria, but that was the last time that name would be used. She preferred, and would be known as, Queen Victoria. Her reign lasted 63 years and 7 months. This is the longest reign of any monarch of Great Britain, and the longest reign of any female monarch in history. Queen Victoria added the title Empress of India in 1876, and ruled the country during its height of power and reach. The period of her reign, 1837 to 1901, is recognized as the Victorian Era. She was succeeded by her elderly son, Edward VII.